In an OFDM receiver with a conventional diversity configuration, one of a plurality of demodulation modules is a master module that solely performs clock recovery and fast Fourier transform window position recovery, the results thereof being used by the other modules as well, so if clock recovery or fast Fourier transform window position recovery falters because of, for example, a drop in the received signal level in the master module, the other modules are also affected and demodulation performance suffers greatly.
A countermeasure is to generate correlation waveform signals for use in clock recovery or fast Fourier transform window position recovery in all demodulation modules, combine the correlation waveform signals of the demodulation modules or select one of them, and perform clock recovery or fast Fourier transform window position recovery from the result, so that these processes do not depend on just one module (see, for example, Patent Document 1).
Combining the respective OFDM signals themselves received through the branches, generating a corresponding correlation waveform signal, and using it in clock recovery or fast Fourier transform window position recovery could also be considered, but with this approach, in order to combine the OFDM signals, it would be necessary to match phases across the branches, which would require a separate circuit to detect phase differences between the respective OFDM signals received through the branches and another separate circuit to correct the phase differences. When, however, the correlation waveform signals are combined, a configuration that does not require detection and correction of the phase differences among the respective signals of the branches is made possible.
Patent Document 1: Japanese Patent Application Publication No. 2001-168833